The Berkeley Evolution Site
Teachers and students who browse the Berkeley site will find resources to aid in understanding and teaching evolution. The materials are organized in various learning paths that can be used in a variety of ways for example "What does T. rex look like?"
Charles Darwin's theory of natural selection explains how animals that are better equipped to adapt biologically to a changing environments over time, and those who do not disappear. This process of biological evolution is the basis of science.
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The word evolution has many nonscientific meanings. For instance "progress" or "descent with modification." Scientifically, it refers to a change in the characteristics of organisms (or species) over time. In terms of biology the change is due to natural selection and genetic drift.
Evolution is an important principle in the field of biology today. It is a theory that has been confirmed by a myriad of scientific tests. It does not address the existence of God or religious beliefs, unlike many other theories of science, such as the Copernican or germ theory of disease.
Early evolutionists, like Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather), believed that certain physical traits were predetermined to change in a gradual manner, as time passes. They called this the "Ladder of Nature" or scala naturae. Charles Lyell first used this term in 1833 in his Principles of Geology.
Darwin published his theory of evolution in his book On the Origin of Species published in the early 1800s. It states that all species of organisms share a common ancestry which can be traced using fossils and other evidence. Related Homepag is the current understanding of evolution that is supported by many lines of research in science that include molecular genetics.
Scientists aren't sure how organisms have evolved however they are certain that natural selection and genetic drift is the primary reason for the evolution of life. People with desirable traits are more likely to live and reproduce, and these individuals pass their genes on to the next generation. As time passes, this results in an accumulation of changes to the gene pool which gradually create new species and forms.
Some scientists use the term"evolution" to refer to large-scale changes, like the evolution of a species from an ancestral one. Certain scientists, including population geneticists define evolution in a broader sense by talking about the net variation in the frequency of alleles over generations. Both definitions are acceptable and accurate however, some scientists claim that the definition of allele frequency is lacking crucial aspects of the evolutionary process.
Origins of Life
The development of life is a key step in evolution. The beginning of life takes place when living systems begin to develop at a microscopic level, like within individual cells.
The origins of life are an important topic in a variety of disciplines, including biology and chemical. The question of how living things got their start has a special place in science since it poses an important challenge to the theory of evolution. It is often called "the mystery of life" or "abiogenesis."
Traditionally, the belief that life could emerge from nonliving things is called spontaneous generation, or "spontaneous evolution." This was a common belief before Louis Pasteur's research showed that it was impossible for the development of life to happen through a purely natural process.
Many scientists still believe that it is possible to go from nonliving substances to living. However, the conditions needed are extremely difficult to reproduce in the laboratory. This is why researchers investigating the origins of life are also interested in understanding the physical properties of early Earth and other planets.
In addition, the development of life is dependent on an intricate sequence of chemical reactions that can't be predicted from the fundamental physical laws on their own. These include the reading of long, information-rich molecules (DNA or RNA) into proteins that perform some function, and the replication of these intricate molecules to create new DNA or RNA sequences. These chemical reactions can be compared to the chicken-and-egg issue which is the development and emergence of DNA/RNA, the protein-based cell machinery, is necessary for the beginning of life. Although, without life, the chemistry required to create it does appear to work.
Research in the field of abiogenesis requires collaboration between scientists from many different disciplines. This includes prebiotic chemists, planet scientists, astrobiologists geophysicists, geologists, and geophysicists.
Evolutionary Changes
The term "evolution" is used to describe the gradual changes in genetic traits over time. These changes could result from adaptation to environmental pressures as described in the entry on Darwinism (see the entry on Charles Darwin for background), or from natural selection.
This mechanism also increases the number of genes that provide an advantage for survival in a species, resulting in an overall change in the appearance of a group. The specific mechanisms behind these changes in evolutionary process include mutation, reshuffling of genes during sexual reproduction, and also gene flow between populations.
Natural selection is the process that allows beneficial mutations to become more common. All organisms undergo changes and reshuffles of genes. As noted above, individuals who have the advantageous trait have a higher reproductive rate than those that do not. This differential in the number of offspring that are produced over a long period of time can result in a gradual change in the average number advantageous characteristics in the group.
One good example is the growing the size of the beaks on different species of finches in the Galapagos Islands, which have evolved different shaped beaks to allow them to more easily access food in their new home. These changes in the shape and form of organisms could also aid in the creation of new species.
Most of the changes that take place are caused by one mutation, but occasionally, multiple mutations occur at once. Most of these changes can be negative or even harmful however, a small percentage can have a beneficial impact on survival and reproduce, increasing their frequency as time passes. Natural selection is a mechanism that could result in the accumulation of change over time that leads to a new species.
Many people confuse the concept of evolution with the idea that inherited characteristics can be altered by conscious choice or use and abuse, which is known as soft inheritance. This is a misunderstanding of the nature of evolution, and of the actual biological processes that cause it. A more accurate description of evolution is that it is a two-step process which involves the separate, and often competing, forces of mutation and natural selection.
Origins of Humans
Modern humans (Homo Sapiens) evolved from primates, a group of mammal species that includes gorillas and chimpanzees. The earliest human fossils indicate that our ancestors were bipeds. They were walkers on two legs. Biological and genetic similarities indicate that we share an intimate relationship with Chimpanzees. In fact, we are most closely related to the chimpanzees within the Pan Genus which includes bonobos and pygmy chimpanzees. The last common ancestor shared between humans and chimpanzees was 8 to 6 million years old.
Humans have developed a range of characteristics over time such as bipedalism, use of fire, and the development of advanced tools. However, it is only in the past 100,000 years or so that most of the essential characteristics that differentiate us from other species have been developed. These include a large brain that is sophisticated and the capacity of humans to construct and use tools, as well as the diversity of our culture.
The process of evolution occurs when genetic changes enable members of a group to better adapt to the environment. This adaptation is driven by natural selection, a process that determines certain traits are more desirable than other traits. People with better adaptations are more likely to pass their genes to the next generation. This is how all species evolve, and the basis for the theory of evolution.
Scientists call it the "law of Natural Selection." The law states species that have an ancestor in common will tend to acquire similar traits over time. This is because these traits allow them to live and reproduce in their environment.
Every living thing has an molecule called DNA that holds the information necessary to direct their growth. The structure of DNA is composed of base pairs that are arranged in a spiral around phosphate and sugar molecules. The sequence of bases in each string determines the phenotype or the distinctive appearance and behavior of a person. Variations in a population are caused by mutations and reshufflings in genetic material (known collectively as alleles).
Fossils of the first human species, Homo erectus and Homo neanderthalensis were discovered in Africa, Asia, and Europe. These fossils, despite a few differences in their appearance, all support the hypothesis of modern humans' origins in Africa. The genetic and fossil evidence suggests that the first humans left Africa and moved to Asia and Europe.